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This is documentation for the next version of K6. For the latest stable release, go to the latest version.

DocumentationGrafana k6JavaScript APIk6/experimentalstreamsReadableStreamCountQueuingStrategy
Open source

CountQueuingStrategy

The CountQueuingStrategy interface of the Streams API represents a built-in queuing strategy that counts the number of chunks in the queue.

Properties

NameTypeDescription
highWaterMarknumberThe maximum number of chunks that the queue can contain.

Example

JavaScript 
import { CountQueuingStrategy, ReadableStream } from 'k6/experimental/streams';
import { setTimeout } from 'k6/timers';

export default async function () {
  // Define a number stream that emits numbers from 1 to 10 every second
  const stream = numbersStream();

  // We use the getReader method to create a reader and lock the stream to it
  const reader = stream.getReader();

  while (true) {
    const { done, value } = await reader.read();
    if (done) break;
    console.log(`received number ${value} from stream`);
  }
}

function numbersStream() {
  let currentNumber = 0;

  // Using the CountQueuingStrategy to limit the number of chunks in the queue to 5
  const queuingStrategy = new CountQueuingStrategy({ highWaterMark: 5 });

  return new ReadableStream(
    {
      start(controller) {
        const fn = () => {
          if (currentNumber < 10) {
            controller.enqueue(++currentNumber);
            setTimeout(fn, 1000);
            return;
          }

          controller.close();
        };
        setTimeout(fn, 1000);
      },
    },
    queuingStrategy
  );
}